Labour MP Geraint Davies has been “administratively suspended” from the party pending an investigation into reports of “incredibly serious allegations of completely unacceptable behaviour”.
The allegations came to light in a report by Politico published on Thursday.
Mr Davies was first elected as an MP in 1997, but was out of parliament between 2005 and 2010.
Shadow immigration minister Stephen Kinnock told Sky News: “I would really urge the women who’ve been affected by this to come forward with formal complaints because if something untoward has taken place, we need them to formally make that complaint so that the whole thing can be investigated in an independent and an efficient and confidential way, based on treating their complains very, very seriously.
“And I do hope that that will happen.
“My understanding is that no formal complaint has yet been made and it’s therefore difficult to move things on.”
A Labour Party spokesperson said: “These are incredibly serious allegations of completely unacceptable behaviour.
“We strongly encourage anyone with a complaint to come forward to the Labour Party’s investigation.
“Any complainant will have access to an independent support service who provide confidential and independent guidance and advice from external experts throughout the process.”